Add repro for #49106
Add repro for #49106

Bug: https://github.com/dart-lang/sdk/issues/49106
Change-Id: Id207cef6b23c75eddbff24bb3e70935998a265f6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/246054
Reviewed-by: Konstantin Shcheglov <09e4d7516628963212bf4aace2f97603d2b706e4@google.com>
Commit-Queue: Paul Berry <72d414e3a99fb120308437779d51667bcc0984eb@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk